U.S. patent application number 15/551927 was filed with the patent office on 2018-02-01 for scissor type compression and expansion machine used in a thermal energy recuperation system.
This patent application is currently assigned to Valeo Systemes Thermiques. The applicant listed for this patent is Valeo Systemes Thermiques. Invention is credited to Jean-Sylvain Bernard, Bertrand Gessier, Abdelaziz Gormat, Stephane Tondelli.
Application Number | 20180030858 15/551927 |
Document ID | / |
Family ID | 53298524 |
Filed Date | 2018-02-01 |
United States Patent
Application |
20180030858 |
Kind Code |
A1 |
Gormat; Abdelaziz ; et
al. |
February 1, 2018 |
SCISSOR TYPE COMPRESSION AND EXPANSION MACHINE USED IN A THERMAL
ENERGY RECUPERATION SYSTEM
Abstract
The invention relates to a compression and expansion machine
comprising a body (12a) with at least one chamber (12) of
revolution about an axis of symmetry, and pistons (14a, 14b, 14c,
14d) rotating about the axis of symmetry and dividing the chamber
into cells (15a, 15b, 15c, 15d) rotating with the pistons, said
machine furthermore comprising a device (22) for coordinating the
movement of said pistons and configured so that, during one
rotation cycle, each cell (15a, 15b, 15c, 15d) performs at least
one first expansion/contraction cycle corresponding to a stage of
compressing a first stream of gas passing through this cell and at
least one second expansion/contraction cycle corresponding to a
stage of expanding a second stream of gas passing through this
cell.
Inventors: |
Gormat; Abdelaziz; (Le
Mesnil Saint Denis, FR) ; Bernard; Jean-Sylvain; (Le
Mesnil Saint Denis, FR) ; Tondelli; Stephane; (Le
Mesnil Saint Denis, FR) ; Gessier; Bertrand; (Le
Mesnil Saint Denis, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Valeo Systemes Thermiques |
Le Mesnil Saint Denis |
|
FR |
|
|
Assignee: |
Valeo Systemes Thermiques
Le Mesnil Saint Denis
FR
|
Family ID: |
53298524 |
Appl. No.: |
15/551927 |
Filed: |
February 19, 2016 |
PCT Filed: |
February 19, 2016 |
PCT NO: |
PCT/EP2016/053604 |
371 Date: |
August 18, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02G 1/02 20130101; F01K
23/065 20130101; F01C 1/063 20130101; F01K 7/36 20130101; F01K
23/14 20130101; F01C 1/07 20130101; F01C 21/18 20130101; F01K 25/10
20130101; F01D 17/105 20130101; F01C 21/008 20130101 |
International
Class: |
F01K 23/06 20060101
F01K023/06; F01K 23/14 20060101 F01K023/14; F02G 1/02 20060101
F02G001/02; F01C 1/07 20060101 F01C001/07 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2015 |
FR |
1551498 |
Claims
1. A compression and expansion machine comprising: a body with at
least one chamber of revolution about an axis of symmetry; pistons
rotating about the axis of symmetry and dividing the chamber into
cells rotating with the pistons; and a coordination device for
coordinating the movement of said pistons, the coordination device
being configured so that, during one rotation cycle, each cell
performs at least one first expansion/contraction cycle
corresponding to a stage of compressing a first stream of gas
passing through this cell, and at least one second
expansion/contraction cycle corresponding to a stage of expanding a
second stream of gas passing through this cell.
2. The compression and expansion machine as claimed in claim 1,
wherein the coordination device is configured such that each cell
performs the same number of first expansion/contraction cycles
corresponding to a stage of gas expansion as second
expansion/contraction cycles corresponding to a stage of gas
compression.
3. The compression and expansion machine as claimed in claim 1,
comprising, in the body, gas inlet and outlet openings for each
cycle of expansion/contraction of the cells, wherein the passage
cross-section of the gas inlet opening is larger than the passage
cross-section of the outlet opening on the first cycle(s), and the
passage cross-section of the gas inlet opening is smaller than the
passage cross-section of the outlet opening on the second
cycle(s).
4. The compression and expansion machine as claimed in claim 3,
wherein the inlet opening of the first cycle is close to the outlet
opening of the second cycle.
5. The compression and expansion machine as claimed in claim 3,
wherein the outlet opening of the first cycle is close to the inlet
opening of the second cycle.
6. The compression and expansion machine as claimed in claim 3,
wherein the inlet opening of the first cycle and the outlet opening
of the second cycle are diametrically opposed relative to the inlet
opening of the second cycle and the outlet opening of the first
cycle respectively.
7. The compression and expansion machine as claimed in claim 3,
wherein the inlet opening of the first cycle and the outlet opening
of the second cycle have a larger cross-section than the outlet
opening of the first cycle and the inlet opening of the second
cycle.
8. The compression and expansion machine as claimed in claim 1,
comprising two pairs of pistons, wherein each cell during one
rotation cycle, performs one and only one first cycle, and one and
only one second cycle, an intake stage of the first cycle on one
cell having a time period common to an exhaust stage of the second
cycle on the cell which follows it in the rotation movement.
9. The compression and expansion machine as claimed in claim 8,
wherein the intake of the first cycle on one cell is offset in time
relative to the exhaust of the second cycle on the cell which
follows it in the rotation movement.
10. The compression and expansion machine as claimed in claim 1,
wherein the coordination device comprises means for coordinating
the movement of the pistons which are fluidically separated from
the chamber of revolution.
11. The compression and expansion machine as claimed in claim 1,
further comprising sealing means between the pistons and the inner
wall of the chamber which are designed to separate the cells and
allow dry friction on the walls of the chamber.
12. The compression and expansion machine as claimed in claim 1,
wherein the cross-section of the chamber on an axial plane is
rounded.
13. A device for recovering energy from a hot thermal source, said
device comprising: a heat exchanger between a working fluid and the
heat source; and a compression and expansion machine as claimed in
claim 1, said device being configured such that at a given instant,
the working fluid returns to the exchanger after having undergone
the compression stage in a first cycle of the machine and leaves
the exchanger in order to undergo the expansion stage in a second
cycle of the machine.
14. The device as claimed in claim 13, wherein the entire stream of
working fluid passing through one of the first cycles is processed
by only one of the second cycles of machine.
15. The energy recuperation device as claimed in claim 13, using a
cycle open to ambient atmosphere.
16. The energy recuperation device as claimed in claim 13, wherein
the exhaust gases of an internal combustion engine form the heat
source.
Description
[0001] The present invention applies to the field of the
transformation of thermal energy into work. More particularly, it
concerns a scissor-type compression and expansion machine intended
to be used in particular in a system causing a fluid to work in
order to utilize the thermal losses of an engine, for example in
the exhaust or any other heat source.
[0002] In fact, despite the improvement in efficiency of engines, a
high proportion of the energy remains lost in the form of heat.
These losses account for the order of 65% in the case of internal
combustion engines running on petrol or diesel. The energy is
released by combustion into the cooling circuit of the engine or
into the exhaust gases which form a heat source relative to the
ambient atmosphere.
[0003] Several types of system using a working fluid heated by this
heat source have been proposed. In all cases, the fluid undergoes a
cycle during which it must be pumped or compressed to enter an
exchanger before then being able to provide mechanical energy by
expansion.
[0004] Certain systems for transforming heat energy into mechanical
energy use a Rankine cycle. This is a closed cycle in the sense
that the fluid is recovered after expansion, cooled and recycled in
order to be compressed before returning to the exchanger.
Furthermore, the fluid (generally water) is in vapor form on
leaving the exchanger with the heat source, then in liquid form
after cooling. These characteristics ensure a good intrinsic
efficiency of systems using this cycle. However, they have a number
of drawbacks, including the need to install a cooling system which
is bulky and consumes part of the cooling thermal flow available
for the internal combustion engine, thus reducing the global
efficiency of the vehicle.
[0005] For this reason, other ways have already been explored with
systems using an open cycle. In this case, the working fluid is
air, which is drawn in at the inlet to the compressor and expelled
to atmosphere after expansion.
[0006] A first embodiment, described in WO12062591, uses a turbine
mounted next to a compressor on the same shaft. The air is
compressed in the compressor, heated by the exhaust gases in the
exchanger, then expanded in the turbine. The energy recovered by
the turbine on the rotation shaft serves firstly to drive the
compressor, and the remainder is available for the desired
applications. The use of a turbine requires a continuous air flow.
To achieve a good efficiency of the turbine, a high flow is
required while retaining sufficient pressure at its inlet.
Furthermore, the rotation speeds are high (over 100,000 rpm).
Turbocompressors adapted to these conditions are generally large,
which leads to a turbine-plus-compressor architecture which is
bulky and costly. Furthermore, the size of a suitable cooling
system would be prohibitive for a small vehicle.
[0007] An alternative embodiment is based on the hot-air piston
engine and uses a Brayton cycle. Typically, in this case, the
system works with two pistons coupled to the same rotation shaft by
their crankshaft. During a rotation, air is drawn in from the
outside into the first piston which lowers, it is then pushed
towards exchanger with the exhaust gases when the first piston
rises again, then expands in the second piston which lowers, and is
finally expelled towards the exterior when the second piston rises.
The piston system accepts rotation speeds which are lower by an
order of magnitude than those of the turbomachine in order to
achieve high pressures and hence an acceptable efficiency. To this
extent, it reduces the integration constraints. However, the
pistons with their air intake systems offer reduced passage
cross-sections for the working fluid. As a result, the pistons must
be large in order to pass the flow necessary to extract the power
released by the exhaust gases. Furthermore, the system uses a
piston and crankshaft system, and a system dedicated to intake and
exhaust of the working fluid, comprising at least one camshaft and
valves intended for opening and closing the inlet and outlet
orifices of the working fluid in the system for transforming
thermal energy into mechanical energy. The result is a complex
system which is still bulky or has a limited power.
[0008] As a variant embodiment of the alternating piston machine,
rotating blade machines are also known for performing compression
and expansion cycles. The blade machine in particular gives high
compression and flow rates, with low rotation speeds and a smaller
size. However, the blade machine remains limited in terms of the
compression rate obtained. Furthermore, it comprises drawbacks with
regard to friction. In fact a seal must be ensured at the point of
contact between the blades and the wall of the working chamber of
the gas, while the movement of the blades comprises a radial
component because of the oval shape of the chamber around the
rotation axis. The support force exerted by the blades against the
wall increases the friction. This drawback is aggravated by the dry
nature of the friction, which avoids polluting the air passing
through the machine in an open circuit with lubricant.
[0009] The object of the invention is to propose a means for
performing the functions of compression and expansion of the
working fluid, which provides high performance in terms of
compression and flow rates while improving the compactness and the
losses due to friction in comparison with a blade machine.
Presentation of the Invention:
[0010] The invention concerns a compression and expansion machine
comprising a body with at least one chamber of revolution about an
axis of symmetry, and pistons rotating about the axis of symmetry
and dividing the chamber into cells rotating with the pistons, said
machine furthermore comprising a device for coordinating the
movement of said pistons, configured such that during one rotation
cycle, each cell performs at least one first expansion/contraction
cycle corresponding to a stage of compressing a first stream of gas
passing through this cell, and at least one second
expansion/contraction cycle corresponding to a stage of expanding a
second stream of gas passing through this cell.
[0011] The characteristics of the compression and expansion machine
in terms of flow and pressure favorably influence the efficiency of
an energy recuperation system in several ways. At the level of the
thermodynamic cycle, this machine--which works on the same
principle of compression or expansion of a gas in a closed cell as
a piston with reciprocating motion--allows high useful pressures to
be achieved with a lower rotation speed than turbocompressors, and
hence a gain in compactness and weight. Also, the large passage
cross-sections allowed by the rotational motion of the cells in the
chamber allows a higher flow and reduces the load losses in the
machine in comparison with pistons of comparable size. Furthermore,
in contrast to the blades of a blade machine, the movement of the
pistons has no radial component. It is therefore easier to design
their interface with the wall of the chamber to ensure the seal
between the cells and to minimize friction.
[0012] Preferably, the coordination device is configured such that
each cell performs the same number of first expansion/contraction
cycles corresponding to a stage of gas expansion as second
expansion/contraction cycles corresponding to a stage of gas
compression.
[0013] This corresponds to an even number of expansion/contraction
cycles performed by the cells. From a mechanical viewpoint, this
can be achieved with two pairs of pistons, the pistons of each pair
moving together. The pistons of each pair are for example
diametrically opposed. Such a configuration may therefore be
achieved with a device for coordinating the piston movement with
simplified architecture.
[0014] Advantageously, the chamber comprises gas inlet and outlet
openings for each expansion/contraction cycle of the cells, wherein
the passage cross-section of the gas inlet opening is larger than
the passage cross-section of the outlet opening on the first
cycle(s), and the passage cross-section of the gas inlet opening is
smaller than the passage cross-section of the outlet opening on the
second cycle(s).
[0015] Advantageously, the machine has at least four openings to
allow the transfer of fluid. At least two openings are provided on
the machine and communicate with the ambient air, and at least two
further openings are also provided on the machine and communicate
with the exchanger. The working fluid pressures are different, such
that the opening cross-sections are adapted accordingly. The
exchange zone with ambient air is known as the low-pressure zone,
and that with the exchanger is the high-pressure zone. Furthermore,
the machine comprises two openings per zone (HP and LP) since the
flow direction is different. For each zone, one opening is intended
for circulation of the working fluid from the interior of the
machine towards the exterior, the other opening allowing its
circulation from the exterior of the machine to the interior.
[0016] Advantageously, the machine comprises two pairs of
pistons.
[0017] According to different variants of the invention which may
be taken together or separately: [0018] the distance between two
openings of a same zone, for example the HP zone or the LP zone, is
smaller than the distance between two openings of two separate HP
and LP zones; [0019] the inlet opening of the first cycle is close
to the outlet opening of the second cycle; [0020] the outlet
opening of the first cycle is close to the inlet opening of the
second cycle; [0021] the inlet opening of the first cycle and the
outlet opening of the second cycle are diametrically opposed
relative to the inlet opening of the second cycle and the outlet
opening of the first cycle; [0022] the inlet opening of the first
cycle and the outlet opening of the second cycle have a larger
cross-section than the outlet opening of the first cycle and the
inlet opening of the second cycle.
[0023] Also preferably, each cell, during one rotation cycle,
performs one and only one first cycle, and one and only one second
cycle, an intake stage of the first cycle on one cell having a time
period common to an exhaust stage of the second cycle on the cell
which follows it in the rotation movement. This allows an increase
in the gas flow passing through the machine.
[0024] The intake of the first cycle on one cell may also be offset
in time relative to the exhaust of the second cycle on the cell
which follows it in the rotation movement. This allows an increase
in the pressure during the stage of heating in the exchanger.
[0025] Advantageously, the coordination device comprises means for
coordinating the movement of the pistons which are fluidically
separated from the chamber of revolution. This configuration allows
correct lubrication of the mechanics of the coordination means and
avoids introducing lubricant into the chamber where the pistons are
rotating.
[0026] Preferably, sealing means between the pistons and the inner
wall of the chamber are designed to separate the cells and allow
dry friction on the walls of the chamber. Because only said sealing
means are interposed between the rotating piston and the inner wall
of the chamber, the fiction area is reduced. Such a reduction is
reflected in an increase in the seal tightness, which allows an
increase in both pressure and efficiency of the machine. Also, in
addition to the dry friction, the air evacuated outside the machine
working in open cycle is not loaded with lubricant particles, such
that the atmosphere is not polluted.
[0027] Advantageously, the cross-section of the chamber on an axial
plane is rounded, for example oval, elliptical or circular. This
allows the design of one-piece sealing means which are more
resistant to wear.
[0028] The invention also concerns a device for recovering energy
from a hot thermal source, said device comprising a heat exchanger
between a working fluid and the heat source, and a compression and
expansion machine as described above, said device being configured
such that at a given instant, the working fluid returns to the
exchanger after having undergone the compression stage in a first
cycle of the machine, and leaves the exchanger in order to undergo
the expansion stage in a second cycle of the machine.
[0029] Said device could be configured such that at a given
instant, the working fluid returns to one of the cells of the
machine during an intake period and leaves from another of the
cells of the machine after having undergone a compression
stage.
[0030] Alternatively or additionally, said device is configured
such that at a given instant, the working fluid returns to the
exchanger after having undergone the compression stage in one of
the machine cells, and leaves the exchanger to undergo the
expansion stage in the same cell or in another of the machine's
cells.
[0031] Also alternatively or additionally, said device is
configured such that at a given instant, the working fluid returns
to the exchanger having undergone the compression stage in one of
the machine cells, and leaves the compression and expansion machine
after having undergone an expansion stage.
[0032] Preferably, in this device, the entire stream of working
fluid passing through one of the first cycles is processed by only
one of the second cycles. This corresponds in particular to a
four-piston machine, which allows a gain in compactness and also
the losses due to friction in the machine, and the complexity of
implementation.
[0033] Advantageously, the energy recuperation device uses a cycle
open to ambient atmosphere. The fluid used is therefore air. In the
case of an application to a motor vehicle for example, the open
cycle has the advantage over a closed cycle that no cooling
exchanger need be fitted in the front part, which would consume
some of the calories for cooling the internal combustion engine.
Furthermore, the cooling circuit requires extraction of some of the
energy for operation. Thus, although the efficiency of an open
cycle is intrinsically lower than that of a closed cycle, the
global efficiency and integration in the vehicle are better.
[0034] In a particular application, the exhaust gases of an
internal combustion engine form the heat source. This is
advantageously the case for installation in a motor vehicle.
[0035] In this device, the working fluid preferably circulates in
counter-current to the exhaust gases in the heat exchanger.
DESCRIPTION OF THE DRAWINGS AND OF THE INVENTION
[0036] The present invention will be better understood and further
details, characteristics and advantages of the present invention
will appear more clearly from reading the description which
follows, with reference to the attached drawings on which:
[0037] FIG. 1 shows diagrammatically the installation of a system
according to the invention for recovering energy from the exhaust
gases of an internal combustion engine.
[0038] FIG. 2 shows diagrammatically a perspective view of a first
embodiment of a scissor-type piston machine according to the
invention.
[0039] FIG. 3 shows diagrammatically a side view of a second
embodiment of the scissor-type piston machine according to the
invention.
[0040] FIG. 4 shows diagrammatically a side view of a third
embodiment of the scissor-type piston machine according to the
invention.
[0041] FIG. 5 shows diagrammatically the function of a scissor-type
piston machine according to the invention in an energy recuperation
system.
[0042] The invention concerns a scissor-type rotating piston
machine designed to be used in an energy recuperation system by
causing a fluid to work in a cycle comprising stages of intake,
compression, heating and expansion, and exhaust, as has been
explained above. The exemplary embodiment of the invention is
presented in the context of integration in a motor vehicle powered
by an internal combustion engine, for recovery of the energy
dissipated by the exhaust gases. However, the applicant does not
intend to limit the scope of his invention to this context, since
it is easy to transpose the type of heat source or energy recovered
to other installations.
[0043] The exemplary system shown diagrammatically in FIG. 1 uses
air as a working fluid in an open cycle. The air is drawn in under
ambient atmospheric conditions before being compressed and then
expelled to atmosphere after expansion. As has been explained
above, this choice is advantageous in terms of integration in the
vehicle but does not exclude the choice of a closed cycle with
cooling of the working fluid in other installations.
[0044] The exemplary system described here comprises: [0045] a heat
source formed by the exhaust gases circulating in the exhaust pipe
1 and originating from the internal combustion engine 2; [0046] a
heat exchanger 3 between these exhaust gases and the air, which is
placed on the exhaust pipe 1; [0047] a compression and expansion
machine 4, performing firstly compression of the air entering the
exchanger 3 and secondly expansion of the hot air leaving the
exchanger 3; [0048] conduits 5 for circulating the compressed air
from the machine 4 towards exchanger 3, and conduits 6 for
returning the air heated in the exchanger 3 to the machine 4;
[0049] conduits 7 for drawing in ambient air to the machine 4, and
conduits 8 for expelling the worked air to atmosphere; [0050] a
drive and energy recuperation system 9.
[0051] In the embodiment shown on the figure, the drive and energy
recuperation system 9 is a means of mechanical transmission between
the shaft 10 of the compression and expansion machine 4, and the
shaft 11 of the engine driving the vehicle, and is intended to
recover the excess torque supplied by the shaft 10. In a variant,
the system 9 may be an electric motor connected to the shaft 10 of
the machine 4 and intended to operate as a generator under the
action of the shaft 10.
[0052] According to a first embodiment, with reference to FIG. 2,
the scissor-type piston machine comprises a hollow body 12a forming
a cylindrical chamber 12 of circular cross-section around an axis
L-L.
[0053] The hollow body comprises four slots forming openings 16,
17, 18, 19 in the chamber 12. On the example, these openings are
made on the outer wall of the chamber 12. They may be segmented,
here into three orifices, over the length of the chamber 12 along
the rotation axis, as shown on FIG. 2. They have an angular
extension defined around the rotation axis and are arranged in
pairs.
[0054] On the example, with reference to FIG. 2 and turning
counter-clockwise: [0055] a first opening 16 is situated at the
bottom and is intended to be connected to the conduit 7 drawing in
ambient air, [0056] a second opening 17 is situated at the top,
substantially vertically above the first opening 18, and is
intended to be connected to the conduit 5 sending the air to the
exchanger 3, [0057] a third opening 18 is also situated at the top,
close to the second opening 17, and is intended to be connected to
the conduit 6 carrying the air leaving the exchanger 3, [0058] a
fourth opening 19 is situated at the bottom, substantially
vertically below the third opening 18 and close to the first
opening 16, and is intended to be connected to the conduit 8
expelling the air to atmosphere.
[0059] Four pistons 14a, 14b, 14c, 14d rotating about axis L-L are
installed inside the chamber 12. They are configured to each occupy
a portion of angular sector, of a given angle, between the outer
cylindrical wall of the chamber 12 and an inner cylindrical surface
13 of circular cross-section transversely to the axis of rotation
L-L.
[0060] These pistons are grouped into two diametrically opposed
pairs of pistons. The pistons of each pair are integral. However,
the two piston pairs may rotate around the axis differently, moving
away or drawing closer. In this way, the four pistons in pairs
define, between the outer wall of the chamber 12 and the inner
surface 13, four cells 15a, 15b, 15c, 15d, the volume of which may
increase or diminish.
[0061] The movement of the two pairs of pistons is coordinated such
that each of the four cells 15a, 15b, 15c, 15d undergoes two
expansion and contraction cycles when passing in front of the four
openings 16, 17, 18, 19 of the chamber 12.
[0062] To achieve this result, a first pair of pistons 14a, 14c is
connected to a first shaft 20 which forms a portion of the inner
cylindrical surface 13 over approximately half the length along the
rotation axis. This first shaft 20 for example is hollow and allows
the passage of the second shaft 21, which forms the cylindrical
surface 13 over the second half of the length along the rotation
axis, and to which the second pair of pistons 14b, 14d is fixed. In
this way, the two pairs of pistons 14a-14c, 14b-14d can be driven
separately in rotation by the two shafts 20, 21.
[0063] The two shafts pass through a transverse face of the wall of
the chamber 12 and, outside this chamber 12, are coupled together
and/or to the shaft 10 leaving the scissor-type machine 4 by a
device 22 coordinating their movements, which allows them to
perform cycles of expansion and contraction of the cells 15a, 15b,
15c, 15d while the shaft 10 of the machine 4 performs a regular
rotation movement. This device for coordinating the movement of the
pistons may be implemented for example by an epicyclic gear
mechanism.
[0064] The point at which the shafts 20, 21 pass through the
chamber 12 is equipped with a sealing means which ensures that the
lubricant used for the mechanisms of the coordination device 22 of
the pistons 14a, 14b, 14c, 14d does not return to the chamber 12.
This therefore prevents polluting with lubricant the air which
passes into the cells and is then expelled into the atmosphere.
[0065] Since each piston has a shape which closely conforms to that
of the inner wall of the chamber 12 and the inner cylindrical
surface 13 created by the two shafts 20, 21, the four cells are
theoretically separated such that the air they contain is either
compressed or expanded depending on the variation in their volume
when they are not passing in front of an opening 16, 17, 18,
19.
[0066] However, the contact points between a piston 14a, 14b, 14c,
14d and the walls of the chamber 12 and the portion of the inner
cylindrical surface 13 created by the shaft 20, 21 to which it is
not connected, are movable. The tightness of a cell 15a, 15b, 15c,
15d between the pistons 14a, 14b, 14c, 14d which delimit it is
advantageously ensured by sealing segments 23 placed on the surface
of said piston and rubbing against the walls on which it
slides.
[0067] It should be noted that the friction losses in the
scissor-type machine, due to the movement of the pistons 14a, 14b,
14c, 14d in the chamber, are therefore linked solely to the sliding
of these segments 23 on the walls. This technology therefore
induces a minimum of losses, in particular because the movements of
the pistons remain tangential to the walls against which a seal
must be provided.
[0068] On the example of FIG. 2, the internal volume of the chamber
12 in which the pistons 14a, 14b, 14c, 14d move has the shape of a
torus of rectangular section. A sealing segment 23 is therefore
formed from four rectilinear portions, two following the parts of
the edge of the piston sliding against the flat faces axially
delimiting the chamber 12, one following the part sliding against
the cylindrical face of the chamber 12, and one following the part
sliding on the shaft 20, 21 which does not rotate in phase with the
piston.
[0069] According to a second embodiment with reference to FIG. 3,
the hollow body 12a is modified such that the walls transverse to
axis L-L of the chamber 12 come to rejoin, with continuity of
tangent, the peripheral cylindrical wall of this chamber.
Furthermore, these transverse walls connect tangentially to the
inner cylindrical surface 13 formed by the outer wall of the two
shafts 20, 21 to which the pistons are attached. The volume in
which the pistons move therefore assumes the form of a torus of
ovoid cross-section, with a rectilinear portion of the
cross-section at the level of the shafts 20, 21 and the outer
part.
[0070] This embodiment allows the production of one-piece sealing
segments which have no joint between two rectilinear portions.
[0071] According to a third embodiment with reference to FIG. 4,
the hollow body 12a and the outer walls of the two shafts 20, 21
are designed such that the volume in which the pistons move assumes
the form of a torus of circular section. This form allows the use
of sealing segments 23 of circular form. The inner surface 13
formed by the walls of the shafts 20, 21 driving the pistons is no
longer cylindrical but has a revolution form created by the
corresponding circle portion. This form allows a better strength of
the segments and ensures a better seal between the pistons and the
walls of the chamber 12.
[0072] With reference to FIG. 5, with the pistons 14a, 14b, 14c,
14d turning counterclockwise, the scissor-type machine 4 causes the
air to circulate discontinuously in the system by
aspiration/pressure of pulses of gas corresponding to the passage
of the cells 15a, 15b, 15c, 15d in front of the openings 16, 17,
18, 19 of the chamber 12.
[0073] The pistons 14a, 14b, 14c, 14d are identical in size, and
the two pairs of pistons 14a-14c, 14b-14d follow the same movement
but out of phase. The four cells 15a, 15b, 15c, 15d therefore
perform an identical cycle during a complete rotation, which is
described below to show how the machine causes the air to
circulate.
[0074] One pair of pistons 14a-14c slows down when approaching the
vertical, on FIG. 5 one of the pistons 14a being between the
opening 16 for intake of ambient air and the opening 19 for
expulsion to atmosphere. During this time, the other pair of
pistons 14b-14d accelerates, such that the piston 14b which has
just passed before the intake opening 16 catches up with the piston
14c of the first pair, placed at the top, and the piston 14d which
has just passed before the opening dedicated to gas returning from
the exchanger 3 catches up with the piston 14a of the first pair,
situated at the bottom.
[0075] In this way, the cell 15a situated between the piston 14a
which has nearly stopped at the bottom, and the piston 14b which is
moving away from there, draws in ambient air through the opening
16. The piston 14a situated at the bottom, by being interposed
between the bottom openings 16, 19, prevents this cell 15a from
drawing in external air through the return opening 19. During this
time, the cell 15b situated between the piston 14c which has almost
stopped at the top and the piston 14b which is approaching this
point, compresses the air it contains and which has just been drawn
in from the ambient air. At a given moment, although its movement
is slow, piston 14c advances and clears the opening 17 for
communication with the exchanger 3, and the air compressed in the
cell 15b can escape towards the exchanger.
[0076] In this way, with reference to FIG. 5, the machine therefore
draws in ambient air at low pressure through the bottom right-hand
opening 16, and expels the air at high pressure through the top
right-hand opening 17.
[0077] Thanks to a symmetrical mechanism, and simultaneously, the
machine draws in high-pressure air from the exchanger 3 through the
top left-hand opening 18, and returns the expanded air at low
pressure to atmosphere via the bottom left-hand opening 19.
[0078] In an offset mechanism, the instants of intake of
high-pressure air from the exchanger 3 through the top left-hand
opening 18, and of return of the expanded low-pressure air to
atmosphere through the bottom left-hand opening 19, are offset in
time. This allows an improvement in the machine efficiency. In fact
the cell 15c situated between the piston 14c which has almost
stopped at the top and the piston 14d which is moving away from
there, is the origin of an expansion of the air it contains. This
air came from the opening 18 connected to the outlet of the
exchanger 3 when the top piston 14c was not blocking the air inlet
opening 18.
[0079] In a similar fashion to the situation between the two
openings 19, 18 at the bottom, the movement of the piston 14c and
its angular size are determined such that it is interposed between
the outlet opening 17 for the high-pressure air and the inlet
opening 18 of the heated high-pressure air. In this way, there is
no mixing between the air passing through the machine 4 on the
right towards the exchanger 3, and the air passing through the
machine 4 on the left and leaving the exchanger.
[0080] The return circuit terminates in the cell 15d situated
between the piston 14a which has almost stopped at the bottom and
the piston 14d which is catching up with it. By contracting, the
cell 15 expels the expanded air to atmosphere through the opening
19.
[0081] It could also be noted that this operating mode separates
the scissor-type piston machine 4--approximately--into a
high-pressure zone in the upper half and a low-pressure zone in the
lower half with reference to FIG. 5.
[0082] The openings 16, 19 of the low-pressure zone are
advantageously adapted to allow the same flow to pass as the
corresponding openings 17, 18 which are situated in the air circuit
but in the high-pressure zone of greater volumic mass. The openings
16, 19 of the low-pressure zone are therefore advantageously larger
than those of the high-pressure zone, since the mass volume of air
passing through them is greater. This allows a large passage flow
through the scissor-type machine 4 and avoids creating parasitic
load losses at the low-pressure openings.
[0083] On the exemplary embodiment presented with reference to FIG.
5, a difference can be seen between the openings 16, 19 of the
low-pressure zone and the openings 17, 18 of the high-pressure
zone.
[0084] The large size of the openings 16, 19 of the low-pressure
zone relative to the angular extension of the piston 14a placed
between them, allows the air intake in the cell 15a on the right
and the air expulsion in the cell 15d on the left to take place
simultaneously over a time period in the machine's operating cycle.
This phenomenon may be useful for promoting the circulation of air
and increasing the flow passing through the machine.
[0085] In contrast, on the example, the relative size of the piston
14c passing at the top and the openings 17, 18 of the high-pressure
zone means that, at a given moment, the piston 14c blocks all
communication between one of these openings 17, 18 and any of the
cells 15b, 15c passing in front of them. In this example, the
phases of air intake from the exchanger 3 into a first cell 15c
through the intake opening 18, and expulsion through the outlet
opening 17 of the air compressed in the cell 15b which follows the
first cell 15c in the rotation movement, take place at two separate
successive moments. Operating variants may be considered, depending
on the relative size of the openings and pistons and of the
position of the openings. However, the pistons all have the same
angular span.
[0086] Other embodiments are also possible by varying the number of
pistons and openings in the chamber 12. However, the number of
pistons and openings shall a priori be a multiple of four, to
ensure that each circuit drawing the air in and sending it to the
exchanger corresponds to a circuit receiving the air from the
exchanger and expelling it to atmosphere.
[0087] The function of the energy recuperation system on start-up
could begin with the scissor-type machine 4 being driven by the
drive and mechanical energy recuperation system 9.
[0088] When the system has begun operation, the global cycle of
five periods may be described by following one of the air pulses
passing through the scissor-type machine 4.
[0089] In a first period, a cell 15a passing in front of the
opening 16 at the bottom right draws in this air pulse taken from
atmosphere by means of the conduit 7, and causes an increase in its
volume at constant pressure.
[0090] In a second period, the cell 15b contracts in volume while
rotating, compressing this air pulse and pushing it into the
conduit 5 through the opening 17. The compression may take place up
to an optimal operating pressure range of between 3 and 12 bar in
the automotive application presented.
[0091] In a third period, this air pulse is transferred to the
air/exhaust gas heat exchanger 3 via the conduit 5. The temperature
rises together with the pressure due to the thermal energy supplied
to the air.
[0092] In the embodiment presented, the air passes through the
exchanger 3 in the opposite direction to the exhaust gases inside
specific conduits. This exchanger arrangement, adapted to the
configuration of the exhaust pipe 1, optimizes the heat exchange
for a given contact distance between the flow of exhaust gases and
the stream of working air. Furthermore, the high pressure level of
the air in the circuit allows a compact design of exchanger 3.
[0093] In a fourth period, a heated and compressed air pulse is
returned to the scissor-type machine 4 via the third conduit 6. The
air enters the machine 4 through the top opening 18 and expands in
a cell 15c, which increases in volume as it rotates.
[0094] With reference again to FIG. 5, the expansion of the hot
compressed air causes the first pair of pistons 14a-14d to rotate
around axis L-L and generates a mechanical energy. The piston
coordination device 22 uses part of this energy to cause a second
pair of pistons 14b-14d to also move, and causes the scissor-type
machine 4 to undergo the first two periods, compressing the pulses
of air arriving in the exchanger. The piston coordination device 22
restores the remaining energy to the rotating shaft 10 leaving the
scissor-type machine 4. The system functions in recuperation mode
as soon as the energy supplied by expansion is greater than the
energy from compression and the losses of the device.
[0095] In the fifth period, by continuing its rotation and
contracting, the cell 15d expels the air pulse towards the conduit
8 for expulsion to atmosphere through the bottom opening 19. At the
end of the expansion, the pressure and temperature of the air fall.
The air is evacuated towards the outside at a temperature of around
100.degree. C.
[0096] The stage of compressing the air in the machine 4
corresponds to the first two cycle periods of intake and
compression, while the expansion stage corresponds to the fourth
and fifth periods of expansion and exhaust.
[0097] A scissor-type machine 4 may achieve pressures of the order
of 3-20 bar with rotation speeds of less than 10,000 rpm.
[0098] With regard to the flow rate, in the example there are four
cells 15a, 15b, 15c, 15d which continuously pass in front of the
openings 14a, 14b, 14c, 14d of the chamber 12. Therefore, the first
period of a cycle begins immediately following the first period of
the preceding cycle. It is not therefore necessary to allow a time
to elapse, as in a four-stroke reciprocating piston machine.
Furthermore, the four periods take place in the same chamber 12,
whereas in comparison, in a reciprocating machine, one piston would
be used for the intake/compression stage of the air coming from
atmosphere, and one piston for the expansion/exhaust stage of the
heated air. The machine is therefore much more compact than a
reciprocating movement piston machine for a same flow rate.
[0099] Furthermore, because of the design of air circulation in the
machine, the openings may be optimized. Because these openings
concern different zones of the chamber, and also because the
rotating means have a continuous movement when passing in front of
them, the geometry of the machine allows the passage cross-sections
to be optimized. These passage cross-sections allow a reduction in
load losses. In comparison with a machine using pistons with
reciprocating movement, such a machine allows a gain of several
factors in the flow rate with lower load losses, which improves the
efficiency of the system.
[0100] Also, in comparison with a blade machine which is another
type of rotating volumetric machine, the configuration allows
further advantages, such as better monitoring of the rate of
compression and expansion of the cells, and hence equivalent
performance to be obtained with a smaller volume.
[0101] In a variant embodiment (not shown), intake air already
compressed passes into the conduit 7 to be drawn into a cell 15a
during the first period of the cycle, which allows a reduction in
the size of the machine for the same performance. For example, the
compressed air may be taken from a turbocompressor which uses the
exhaust gases as a source for driving the compressor in
rotation.
[0102] In another variant embodiment (not shown), the intake
air--either ambient air or compressed air--is first cooled before
entering the machine via an intake air cooler for example, which
allows a reduction in the temperature of the working fluid entering
the exchanger, and hence an increase in efficiency of the energy
recuperation device.
[0103] In fact, to operate optimally, the temperature of the
working fluid on entry to the exchanger must be lower than the
temperature of the heat source circulating in the exchanger.
[0104] In the context of an application to a vehicle powered by an
internal combustion engine, the system will be furthermore
advantageously adapted to the variations in engine speed or
atmospheric conditions, for example by introducing bypass-type
systems on the air circuit and on the exhaust pipe for the engine
gases upstream of the heat exchanger, in order to adapt the flow
rates to the energy which may be recovered. Also, in a variant,
with a view to optimizing efficiency, additional cooling of the
rotating volumetric machine by a water or air circuit or by fins
may prevent excessive heating thereof from friction and from the
working fluid coming from the exchanger.
* * * * *